This invention relates to tufting machines, and more particularly to a drive arrangement for a yarn feed roller pattern assembly having a plurality of feed roller sets, cooperating roller sets being drivingly connected with a selected one of a number of continuously driven shafts for rotating at a respective and different speed, thereby to deliver yarn to the tufting machine in accordance with patterning requirements.
Wide use is made of yarn feed roller pattern attachments or assemblies for producing variations in pile height in tufted pile fabrics such as carpeting. Representative of such feed roller pattern assemblies are those disclosed in the following U.S. Pat. Nos. 2,862,465 to Card; 2,875,714 to Nix; 2,966,866 to Card; 3,001,388 to MacCaffray; 3,075,482 to Card; 3,103,187 to Hammel; 3,134,529 to Beasley; 3,272,163 to Erwin, et al; 3,489,326 to Singleton; 3,605,660 to Short; 3,752,094 to Short; 3,847,098 to Hammel; 3,926,132 to Lear, et al; 3,955,514 to Prichard, et al and 4,134,348 to Scott.
These assemblies include a plurality of yarn feed rollers which feed yarn to the needles of the tufting machine. Each of the feed rollers is selectively driven at one of a plurality of different speeds independently of the other feed rollers by means of clutches controlled by a pattern control. The amount of yarn supplied to the needles of a tufting machine is determined by the rotational speed of the feed rollers about which the yarn is wound, so that with a fixed needle stroke the amount of yarn supplied to each needle determines the pile height of the fabric produced. To create patterned pile effects the amount of yarn fed to the individual needles may be varied by driving the feed rollers selectively at the different speeds.
Early in the development of yarn feed roller pattern assemblies, such as exemplified in Card U.S. Pat. Nos. 2,862,465 and 2,966,866, the feed rollers were mounted in parallel relationship upon respective shafts extending perpendicularly to the row of needles, and each shaft carried a high speed clutch and a low speed clutch. All of the high speed clutches were driven by chain and sprocket mechanisms from a high speed shaft, while all of the low speed clutches were driven by another chain and sprocket mechanism from a low speed shaft, one or the other of the clutches being selectively engaged to couple its drive to the shaft. Later in the development of the prior art, the rollers were separated into upper and lower roll sets with each roll set coupled to a drive shaft, each drive shaft carrying a high speed clutch and a low speed clutch. Again, all the high speed clutches were driven by chain and sprocket mechanisms from a high speed shaft and all the low speed clutches were driven by a chain and sprocket mechanism from a low speed shaft. Actuation of a respective clutch selectively coupled its drive means to the drive shaft to rotate the rolls of each set to the respective high or low speed shaft. Such constuctions are exemplified by Hammel U.S. Pat. Nos. 3,103,187 and Erwin, et al 3,272,163.
The electromagnetic clutch members of the feed roller assemblies wear out or become defective before other parts thereof, and considerable dissassembly of these prior art drive mechanisms had to be carried out before the clutches could be replaced. Such dissassembly and replacement resulted in considerable "down-time" which in many cases was well out of proporation to the seriousness of the fault.
To reduce such "down-time" the prior art developed yarn feed roller assemblies in which the clutch is within the roll. For example, in U.S. Pat. Nos. 3,489,326 to Singleton and 3,926,132 to Lear, et al the clutches were placed within respective rollers. Here two or more drive shafts are driven at different speeds each carrying a number of feed rolls rotatable relative to the respective shafts. Corresponding rolls on each shaft form a roll set which are coupled together so that each set of rolls may rotate at the same speed. The clutches are selectively engaged to couple the roll associated with the engaged clutch to the shaft on which the clutch is mounted for driving that roll and the other rolls in that set from the shaft carrying the engaged clutch. A number of shaft sections were coupled end to end so that a shaft section may be removed for repair or replacement of a defective clutch. However, although highly succesful and effective in reducing "down-time" problems still resulted from the handling of a large number of feed rolls and clutches on a single shaft section. If a clutch in the middle feed roll of a shaft section is defective, then all the remaining feed rolls and clutch members between the defective clutch and the end of the shaft section must be removed before the problem can be remedied. Moreover, since the rolls are removed with the associated clutches, the yarn wound about the rolls is disturbed and when a shaft section is replaced the yarn must again be threadedly wound about the rolls in each roll set associated with the replaced shaft section.
In another effort to reduce the "down-time" a module construction was proposed in Hammel U.S. Pat. No. 3,847,098 wherein each roll set is mounted within a modular housing having a chain and sprocket drive for each roll of the set, with each drive being operable to connect a first shaft on which each roll of the set and its associated internal clutch is mounted to another shaft which carries a gear extending from the module. The latter gears are coupled to a corresponding gear mounted on a shaft in a drive housing when the module is mounted in an operative position. Actuation of one of the clutches within the module couples its roll and by virtue of gearing between the rolls in a set, all the rolls, in the set to the drive and thus the shaft within the drive housing associated therewith. When a clutch must be replaced or repaired, the module including the associated rolls, clutches, chains and sprocket drive is detached and replaced as a unit. Although a more convenient arrangement is provided for changing a worn-out clutch in a module by replacing the entire module, all the rolls, clutches, gears and drive members are removed with the moudle, and the yarn associated with the replaced module must still be pulled away from the original module and then threadedly rewound about the replacement unit, albeit only the yarn associated with that module need be disturbed. Moreover, because of the bulkiness of the modules, they must be mounted in groups spaced vertically apart so as to provide the required number of modules for a tufting machine. This is an inconvenience in servicing the rollers as when the yarn is initially threaded about the various rollers of the yarn feed assembly since it requires working at two different levels, one of which requires a ladder. Furthermore, the size of the rolls are limited by the size of the clutch, as with any yarn feed roller attachment having the clutch within the rolls. This limits the size of the clutch and its associated elements, thereby resulting in faster wearing characteristics since the size of the rolls must be large enough to receive the clutches, the rolls are of a larger size than necessary resulting in the yarn feed attachment being placed high up on the tufting machine, adding to the inconvenience of threading the yarn about the rollers, and of servicing the modules.